1. Field of the Invention
The present invention relates to a light source unit and a projector which includes the light source unit.
2. Description of the Related Art
In these days, data projectors are used on many cases as image projection apparatuses which project images including images of screens and video images of personal computers, as well as images based on image data which is stored in memory cards on to a screen. These projectors are such that light emitted from a light source is collected to a micromirror device called DMD (Digital Micromirror Device) or a liquid crystal plate for display of a color image onto the screen.
In projectors of the type described above, conventionally, projectors using a high-intensity discharge lamp as a light source have been the mainstream of projectors. In recent years, however, there have been made many developments and proposals on light source units which utilize a semiconductor light emitting device such as a light emitting diode (LED), a laser diode (LD), or a device utilizing organic EL technology, luminescent emission as a light emitting device of a light source unit. For example, Japanese Unexamined Patent Publication No. 2004-341105 (JP-A-2004-341105) proposes a light source unit having a luminescent wheel and a solid-state light source, the luminescent wheel being made of a circular disk-shaped transparent base material on which luminescent material layers are disposed which receive ultraviolet rays emitted from the solid-state light source as excitation light to convert them into visible light.
In the proposal described in JP-A-2004-341105, ultraviolet rays are shone as excitation light on to the luminescent material layers formed on a surface of the luminescent wheel, whereby the luminescent material layers become luminous so as to emit luminescent light rays of red, green and blue wavelength bands. However, the luminous efficiency of the red luminescent material is lower than those of the other luminescent materials. Due to this, in the event that respective ratios of the luminescent material layers which are disposed in a circumferential direction of the luminescent wheel are made substantially the same, there is caused a problem that the luminance of red becomes insufficient.